A general consensus has arisen within the television broadcast industry that a television picture being displayed should have an aspect ratio of roughly 16 units wide by nine units high (1.777). This desireably wide aspect ratio is quite different from the present 4 units by 3 units (1.333) aspect ratio of the conventional television picture. Thus, there is a basic artistic incompatibility between the proposed wide aspect ratio (1.777) and the existing, conventional aspect ratio (1.333).
Different approaches have been proposed in order to solve the incompatibility between these two aspect ratios. The present inventor has proposed a compromise, namely an aspect ratio of about 1.6, which lies between the wide aspect ratio and the narrow, conventional aspect ratio. With this approach, and taking into account the common practice of overscanning the television display device, a very little black band appears at the top and bottom of the picture. It is vaguely compatible and be somewhat wider than the conventional 1.333 ratio. This approach has not met with widespread acceptance. In the vernacular, it is neither fish nor fowl, and is not seen to provide the aesthetic quality to the picture obtainable with the 1.777 wide aspect ratio.
Two approaches have been proposed. Workers at the David Sarnoff Center have proposed a side panel approach in which side panel information from both sides of the picture image is packed into spectral space within the existing bandwidth, or is contained within the spectrum of an adjacent channel. While this approach is downwardly compatible, the implementation is very complicated and expensive, and receivers adapted to make use of the additional side panel information are also very complicated and expensive.
The other approach is known as a letter box approach. In this approach a letter box pattern is presented on the screen (horizontal black bands at the top and bottom of the picture). On new wide aspect ratio displays, the full display screen is filled. And, the horizontal black bands at the top and bottom of the picture display on the old, conventional display may be filled with augmentation signals to improve resolution or reduce noise in the visible picture. The present inventor's U.S. Pat. No. 4,959,717 provides a description of a method for masking reinforcement signals in the horizontal bands resulting from the letter box approach.
Workers at NTV have proposed a compromise between the side panel approach and the letter box approach. In the downwardly compatible mode, an aspect ratio of about 1.6 is presented, and on new television display devices a full 1.777 wide aspect ratio is presented. The NTV approach makes use of pixel thinning out techniques for thinning out the number of pixels on the side panels, so that low frequency pixel components (one third) remain in the side panels and the high frequency pixel components (two thirds) are moved to scan lines at the top or bottom of the picture which are not so visible on account of overscan. This approach is outlined in a paper presented by Y. Kimata, Y Araki and S. Takayama of Nippon Television Network Corp., Tokyo, Japan (NTV) at the National Association of Broadcasters in Atlanta, Ga. on Apr. 2, 1990 and entitled "Study of the Methods of Signal Processing Applicable to the Wide Aspect EDTV Compatible with NTSC". While this approach has been demonstrated to be feasible, the implementation on a pixel thinning basis is complicated and expensive at both encoder and decoder.
Thus, a hitherto unsolved need has arisen for a wide aspect ratio television system which is asethetically compatible with existing conventional 1.333 aspect ratio picture displays and which enables an enhanced wide aspect ratio display to be realized at far greater simplicity and lower cost than heretofore.